What could be causing blurred vision in one eye and how is it treated?

Blurred Vision in One Eye: Causes and Treatment

Blurred vision in one eye requires urgent evaluation to rule out sight-threatening and life-threatening conditions, with the most critical being retinal artery occlusion, retinal detachment, acute angle-closure glaucoma, giant cell arteritis, and optic neuritis—all of which demand immediate ophthalmologic assessment and intervention. 1, 2, 3

Immediate Life- and Sight-Threatening Causes to Rule Out First

Retinal Artery Occlusion

• Presents as sudden, painless vision loss in patients with vascular risk factors (atherosclerosis, carotid disease, cardiac emboli) 1, 3
• Requires urgent stroke evaluation and immediate therapy to lower intraocular pressure with agents like acetazolamide and vasodilating medications to minimize retinal ischemia 1
• Interventions primarily aim to prevent vision loss in the fellow eye, as affected eye prognosis is often poor 1

Retinal Detachment

• Characterized by a curtain-like visual field defect, often preceded by floaters and flashing lights 1, 3
• Requires immediate ophthalmology referral for dilated funduscopic examination and usually necessitates surgical intervention 1, 3
• Any patient with symptomatic floaters and flashing lights must be referred urgently to evaluate for retinal tear or detachment 3

Acute Angle-Closure Glaucoma

• Features ocular pain, headache, nausea, and blurred vision 1
• Treatment includes pilocarpine eye drops, oral or intravenous acetazolamide, and intravenous mannitol 1
• Represents a true ophthalmologic emergency requiring immediate intervention 1

Giant Cell Arteritis (GCA)

• Should be suspected in patients older than 50 years with scalp tenderness, jaw claudication, proximal muscle and joint pain, and constitutional symptoms 1
• Elevated C-reactive protein, erythrocyte sedimentation rate, and platelet count support the diagnosis 1
• Requires immediate initiation of empiric high-dose steroids to prevent vision loss in the unaffected eye, even before temporal artery biopsy confirmation 1

Optic Neuritis

• Presents with color desaturation, relative afferent pupillary defect (RAPD), and pain with extraocular muscle movements 1
• Treatment requires high-dose steroids, and patients should be evaluated for multiple sclerosis 1
• Can present with subtle vision loss and optic disc swelling 4

Common Non-Emergent Causes

Refractive Errors

• Myopia causes difficulty seeing distant objects clearly while near vision remains preserved 5
• Hyperopia affects near vision primarily, though distance vision may be impaired depending on accommodative ability 5
• Astigmatism causes blurred or distorted vision at all distances due to irregular corneal curvature 5
• A pinhole test rapidly distinguishes refractive causes from other pathology—improvement with pinhole suggests refractive error as primary etiology 5

Ocular Surface Disorders

• Dry eye syndrome causes intermittent blurred vision, often worse upon waking and improving later in the day, with burning and foreign body sensation 5
• Tear film instability disrupts the optical surface, leading to fluctuating vision 5

Cataract

• Causes gradual progressive blurred vision, glare disability, and reduced contrast sensitivity 5
• Glare disability with relatively preserved acuity is characteristic 5
• Posterior capsule opacification can occur after cataract surgery, causing gradual vision decline 5

Corneal Edema

• Presents with blurred vision showing diurnal variation—worse upon waking, clearer later in the day due to evaporation 5, 6
• Can be caused by topical corticosteroids elevating intraocular pressure 5

Binocular Retinal Diplopia (Macular Disease)

• Retinal disease causing foveal distortion (epiretinal membranes, subretinal membranes, macular detachment) can cause blurred vision and diplopia 7
• Develops within days to weeks of maculopathy onset and rarely improves spontaneously 7
• Fogging of one eye using Bangerter foils or Scotch Satin tape is the most successful long-term treatment, eliminating foveal conflict by producing a central scotoma 7
• Prism correction provides only transient relief in most cases 7
• Surgical membrane peeling improves diplopia in only a proportion of patients and may cause new diplopia in others 7

Diagnostic Approach Algorithm

Step 1: Assess Acuity and Timing

• Sudden onset (minutes to hours): Consider vascular occlusion, retinal detachment, acute glaucoma, GCA 1, 2, 3
• Subacute (days to weeks): Consider optic neuritis, infiltrative processes, macular disease 1, 4
• Gradual (months): Consider cataract, refractive error progression 5

Step 2: Characterize Pain and Associated Symptoms

• Painful with eye movement: Optic neuritis 1
• Painful with headache/nausea: Acute angle-closure glaucoma 1
• Painless: Retinal artery occlusion, retinal detachment, cataract, refractive error 1, 3
• Scalp tenderness, jaw claudication in patient >50 years: Giant cell arteritis—start steroids immediately 1

Step 3: Perform Targeted Examination

• Pinhole test: Improvement suggests refractive error 5
• Pupil examination: RAPD indicates optic nerve or severe retinal disease 1, 4
• Visual field testing: Curtain-like defect suggests retinal detachment 1
• Slit-lamp examination: Evaluates cornea, anterior chamber, lens 5
• Dilated funduscopic examination: Essential for retinal detachment, vascular occlusion, optic nerve pathology 3

Step 4: Consider Age and Risk Factors

• Age >50 with systemic symptoms: Rule out GCA first 1
• Vascular risk factors: Consider retinal artery occlusion, amaurosis fugax from carotid disease 1, 8
• Leukocytosis with optic disc swelling: Consider infiltrative optic neuropathy from leukemia 4

Treatment Principles

Emergent Conditions

• Do not delay treatment for confirmatory testing in suspected GCA—empiric steroids prevent irreversible vision loss 1
• Immediate ophthalmology referral for retinal detachment, acute glaucoma, and suspected vascular occlusion 1, 3
• Globe injuries require metal shield coverage and prophylactic oral antibiotics to prevent endophthalmitis 3

Non-Emergent Conditions

• Eyeglasses are the simplest, most cost-effective correction for refractive errors and should be considered before contact lenses or surgery 7
• High-index lenses reduce thickness and weight for high refractive errors, improving comfort and cosmesis 7
• Contact lens wearers should have backup eyeglasses to prevent overwear complications 7

Critical Pitfalls to Avoid

• Never use topical corticosteroids empirically for periorbital swelling or blurred vision without slit-lamp examination, as they can worsen infectious causes and elevate intraocular pressure 6, 9
• Latanoprost and other glaucoma medications can cause blurred vision, corneal edema, and macular edema as adverse effects 9
• Do not dismiss transient monocular vision loss (amaurosis fugax) as benign—it represents TIA from carotid or cardiac emboli requiring urgent stroke workup 8
• Patients with macular disease and diplopia often have peripheral fusion that conflicts with foveal misalignment—correcting measured strabismus with prisms or surgery rarely resolves symptoms 7
• Comprehensive medical eye evaluations should occur every 5-10 years for patients under 40, every 2-4 years for ages 40-54, every 1-3 years for ages 55-64, and every 1-2 years for those 65 and older 7